Exploring antisemitism: Israeli filmmaker Yoav Shamir on set during the making of his documentary Defamation, 2009 Photograph: Everett Collection/Rex Featu/Rex Features

How is it that so many people who care deeply and genuinely about the problem of antisemitism find themselves on the opposite sides of a barricade fighting what sometimes seems like a war to the death? How many of us who have got caught up in these often bitter battles have hoped for some way of finding a common language through which we could discuss our differences?

Zionism and the state of Israel were supposed to have eliminated antisemitism, so "Why do the words Holocaust, Nazis and antisemitism appear so often in the Israeli press?" asks Shamir. Antisemitism is on the rise, he is told. To investigate this, he uses a cool, slightly ironic, but engaged style. He spends most of his time either observing and talking with Abe Foxman, veteran head of the US Anti-Defamation League (ADL), the largest Jewish organisation combating antisemitism worldwide, or accompanying a group of Israeli senior high school students who go on the March of the Living, a trip to the death camps in Poland made each year by 30,000 youngsters.

The ADL sees antisemitism rising everywhere. From Foxman, Shamir learns that the only answer is to stamp on it hard by playing on feelings of guilt about the Holocaust. Heavy-handed and exaggerated? Privately, even some senior ADL lay supporters think so. And when Shamir tries to explore what the rise in antisemitism consists of, he finds it rather elusive. Foxman and ADL officials tell him there's been a spike in US antisemitic incidents, which are now running at 1,500 a year, but when he asks them to identify a recent local one, where the physical evidence could be filmed, most appear to be very minor.

He also learns that the Israeli students are indoctrinated with an exaggerated sense of the danger of antisemitism in Poland. "We're raised to know that people hate us," says one. Another wants to absorb the mantra he hears from his parents: "Never forgive, never forget." Before they leave for Poland they are briefed: "You will not have contact with the local people," it's too dangerous.

Shamir shows us that the threat of another Holocaust looms large both for the wealthy, elderly ADL supporters who go on international missions with Foxman and for the Israeli high school students. The former stand at Babi Yar in Kiev, where tens of thousands of Jews were massacred in 1941, and one woman says: "The worst thing standing here is that it could happen again today." The students go to Auschwitz and believe the Israeli secret serviceman who tells them they're in "hostile country" and can't go out from their hotel in the evening because neo-Nazis will attack them.

The ADL works very closely with the Israeli government in spreading the notion that the "new antisemitism" – extreme and unfair hostility to Israel – is the principal danger today. When Shamir asks whether there is any possibility that Israel's actions may lead to antisemitism, Foxman says: "It's nonsense." This orthodoxy is displayed at a conference of the Global Forum for Combating Antisemitism in Israel. So, when Dr David Hirsh, from Goldsmiths, University of London, and founder of Engage, who agrees that there is a "new antisemitism", bravely speaks of the iniquity of settlements and occupation and their role in making people hate Israel, he's suddenly treated like a pariah. Professor Dinah Porat, who runs an antisemitism research centre at Tel Aviv University, tells him: "I don't get it, unless you were being ironic." Shamir concludes: "Speaking with Dr Hirsh made me realise it's hard to say anything different."

This message is central to the film. Shamir finds people having difficulty saying something different about antisemitism without then being branded as giving succour to antisemites.

Shamir lets the camera, and a few carefully chosen words of his own, imply criticism and sympathy, often both at the same time. He's unhappy with those who fetishise the Holocaust, use antisemitism to hold Israel and the Jewish people back from living in the present and looking to the future, and deny that Israel's behaviour towards the Palestinians plays a role in determining hostile attitudes to Jews. He questions Foxman's methods and is deeply troubled by the attitudes of the students, but he shows sympathy for both.

He never denies that antisemitism exists today and he encounters real, if rather confused, antisemitic attitudes on the streets of New York. But the film suggests there is more than one truth about antisemitism: yes, it's true that antisemitic incidents continue to occur, but it's also true that their significance is determined by the context in which they occur. If we could come together around this conclusion, we might find the common language required to bridge, but not deny, genuine differences. It's a deceptively simple message, but one that pleads for openness and an awareness of the complexity of antisemitism.

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